Studies involving neuron specific enolase (NSE) have during the past year focused on the clinical application of this new methodology. Studies on small cell lung cancer patients have continued with our previous serum data being validated. The diagnostic value of NSE in pediatric neuroblastoma patients has also been shown with 96% of Stage IV patients displaying highly elevated serum NSE levels. Serum NSE level is also predictive of survival time, especially in the infant to one-year-old patient group. We have shown that NSE radioimmunoassay and immunohistochemistry is able to identify virtually all neuroendocrine, APUD cells as well as tumors (APUDomas) derived from these cells. Basic studies have shown NSE to be a good index of neuronal regeneration with levels decreasing in brain areas that are innervated by damaged nerves.